Types of Tappets for Diesel Generator Sets

The camshaft driven tappet is a component of the valve transmission mechanism, also known as the valve tappet, which is used to follow the contour of the cam on the camshaft for movement. The valve tappet is directly driven by the camshaft, converting the rotational motion of the camshaft into reciprocating motion to open and close the valve. At present, diesel generator sets have integral sliding type tappets, cam follower (roller type tappets), roller arm type and hydraulic type tappets.

Integral sliding strut

Integral tappets transmit motion in the form of a single integral component, commonly found in small generators. To reduce the weight and inertia of the push rod, some integral tappets are designed as hollow tubes, while others are designed as solid. The integral strut is mainly used on older engines or some high-performance engines. One disadvantage of it is that it has high noise and a special knocking sound.

All engines with integral tappets must have measures to adjust the valve clearance. When the valve comes into contact with high-temperature gas, it expands due to heating and elongates along the valve stem. The longer the valve stem, the greater the expansion. If there is no gap between the tappet and the valve foot or between the rocker arm and the valve foot during the transmission process, the internal combustion engine will not work for long, and the valves will leak due to poor closing.

Roller type strut

Roller type tappets are equipped with a small roller at their lower end, so that when the cam hits the roller, the roller rolls on the convex curve, reducing direct wear between the tappets or cam. They are mainly used in high compression ratio engines and are similar to integral tappets, with the only difference being that the cam follower rolls on the camshaft through the roller instead of sliding through metal. The cam follower reduces friction and distributes the load more evenly.

Roller arm type tappet

Replacing the tappet with a rocker arm with a roller between the cam and the tappet is called a roller arm. One end of the roller arm is fitted onto a shaft parallel to the camshaft, which is called a roller shaft. Replacing the tappet with a roller arm can reduce the lateral pressure of the camshaft on the tappet and the reciprocating inertia force of the tappet.

Hydraulic tappet

Hydraulic tappets (columns) can reduce noise and control valve clearance: Hydraulic tappets maintain valve clearance at zero through oil pressure. Hydraulic tappets are mainly composed of tappet housing, oil hole, plunger spring, spring seat, spring, one-way ball, plunger, metering valve, tappet seat, and lock ring.

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